The flight to Samui is outrageously pricey compared to the Tiger, Air Asia deals to Phuket, Krabi and elsewhere around the region. BKK airlines owners are making a mint, but as there is no other way to get there....
That said, Samui is fab if you keep away from Chaweng, Lamai etc.
There are some absolute gems of hotels etc in the SW and NE parts of the island. SW is really really quiet and beautiful. NE is more developed but very upmarket (Six Senses etc).
Personally I love the SW. The beaches are MUCH nicer than anywhere else.
http://www.bansabaisunset.com/
If you do want to stay in a place with a bit more life then BoPhut, Lamai and Chaweng are the go. However, I dont rate the beaches in any of those locations (BoPhut is prolly the best of the 3). The island is pretty small tho and renting a car, or motorbike to get around is very cheap.
If you have a bit of dosh to throw around this is one of the best hotels/resorts on the island (but its a detox zone)
http://www.kamalaya.com/